2009 KLX 250s, 351 kit and pumper carb from Bill Blue. 4k miles on the install. No start. Cranks over, wont' fire up even with starting fluid. Not the starter or battery. Plug is sparking. Cranks over at the same speed plug in or out. Has anyone had a failure of the compression release? I will be checking valve clearance, would incorrect valve clearance cause a no start? Going to access it
friday morning first thing to check the valves and see if anything stands out. Any tips or experience?

 

Did you do any other service or have an issue immediately before this problem started...or didn't start, LOL! Something like the bike sitting for a long period, etc. Had the bike been starting perfectly or did you detect a slower and slower starting cycle until it just quit starting?

On your valve question...yes...valve clearance gets tighter as they wear, and it "can" get to a point where compression fails to allow engine start. There's usually a little lead up to this point warning you that your valves are tight...slow starting. The KACR to ease starting can fail...rarely...but it's not usually causing the engine to lose compression...it usually quits releasing any compression. I think you're right to check your valves and see if the KACR components are all still in place.

Sounds like you're getting fuel (or starter fluid), spark, and air. You didn't mention "air", but that's an easy one to check. I sheepishly admit to showing up at a state circuit enduro race and not being able to start my 1976 Husky 360 Auto the evening before to check out the test track. After an hour of fouling 2 plugs and scratching my head, I found the rolled up athletic sock stuffed in the airbox boot to keep things clean while I had cleaned the filter back at home. It can happen...LOL!

 

If it's a case of it ran fine and then didn't start, I doubt that there's a mechanical issue.
I had a similar issue on my 351 and it turned out to be just a bad spark plug.
I would also inspect the primary wiring connections for the ignition coil. Both the circuit from the ignitor and the ground connection on the coil bracket.

 

He states the plug is sparking...I assume he grounded the plug to the engine to do the conventional test for spark we usually do. However, there are conditions occasionally where an ignition system is weak enough to allow spark but not when the plug is under compression in a chamber. It's not super common, but I have seen it.

 

I've had plugs that seem to be fine, but are not. Easy to check with a new plug, IMO. Then you have a spare.
Did the bike sit for a long time? If so, carb needs cleaning. If you have the stock carb, you could have some other failure there in the lift slide.

 

This was the cause of the no-start. I put the stock carb back on and the problem went away. Are there any videos showing the disassembly of this carb? I would like to get it working again and put it back on. any advice would be appreciated.

TKX

 

If you are not going to ride your bike for a couple of weeks, turn the fuel off and run all the gas out of the carb when you shut it down. Irregardless of the type of carb.

 

Yep, good advice, been doing it for about 30 years or so since the Government has been fuc$ing with our gas.

 

I swapped the pumper carb with the stock OEM carb and the problem went away. Now to figure out the carb, do a rebuild kit I think.

The Mick